Most people have at least seen, if not actually used, a hand-held ("walkie-talkie") portable two-way radio. Hand-held radios have revolutionized the way some people work. For example, a police officer can bring a hand-held radio when investigating on foot--thereby increasing safety and effectiveness due to the ability to instantaneously communicate with a dispatcher or other police officers. Fire and rescue workers, paramedics, power and telephone company field technicians, and other people performing tasks critical to general safety and welfare greatly benefit from hand-held two-way radios.
Smaller is generally better when it comes to hand-held radios. Smaller radios are more convenient to carry, reduce user fatigue, and may be able to go places that larger radios cannot go. For example, undercover police officers are not able to carry large two-way radios since such radios could be easily seen and thus "tip off" criminals and others under investigation. A radio small enough to fit into the officer's front shirt pocket could be concealed underneath a normal jacket and thus could actually be carried by the police officer during covert and undercover operations. The ability of a police officer to carry such a two-way radio while undercover would greatly increase the officer's safety and undercover operations. However, various problems have in the past prevented such a compact full-featured radio from being widely produced.
Recent innovations in custom chip design allow radio designers to eliminate circuits, reduce the number of components and cut power drain. Thus, it is now possible to provide a full-featured digital radio transceiver in a very small, low profile package. However, battery miniaturization has not kept up with advances in semiconductor miniaturization. Whereas only a few years ago the size and weight of the battery constituted only a small percentage of the overall size and weight of a hand-held radio, the battery may now comprise a significant percentage (on the order of half) of the radio's size and weight.
Hand-held radios have long been powered by removable rechargeable battery packs that attach to the lower portion of the radio housing so as to become part of the radio hand grip. Such detachable reusable battery packs allow users to easily swap a recharged battery for a "dead" battery pack. The "dead" pack may then be recharged without removing the radio from service during the recharge procedure. Once charged, a battery pack should last at least as long as a typical work shift (e.g., eight hours) so that the radio user does not need to carry additional battery packs and/or swap batteries in the middle of a shift.
As everyone who has ever bought a flashlight knows, larger batteries deliver more current and thus have a longer life (assuming constant current draw). For example, a size "D" flashlight cell delivers several times the amount of current delivered by a much smaller "AA" penlight flashlight cell, and may thus power a lamp for a longer time (or power more powerful lamp for the same amount of time). However, the larger "D" cells are also several times more bulky and heavy as compared to penlight cells. If the amount of current continually being drawn by a radio from the battery can be decreased, then the radio can operate for a longer time on a single battery charge. Moreover, very low current consumption means that even a relatively small battery can be used to provide relatively long periods of operation.
Unfortunately, the sophisticated features provided on today's two-way radios require large amounts of software. This software can best be developed and maintained using high level languages such as C. However, these languages require high performance microcontrollers for proper execution speed.. These controllers require a great deal of current.
Some past designs have used multiple low performance microcontrollers, but such constructions prevent the use of high level languages and their advantages in development time and maintainability. Other designs have used a single low power microcontroller with custom hardware. This solution suffers from the same problems as multiple low performance controller technique, and also is not very flexible since the functions of the custom hardware become fixed once the custom hardware design is finalized. Other prior art designs may use the "sleep mode" of a processor to turn off the CPU, but may keep the peripherals running.
The present invention, in contrast, provides a miniaturized two-way radio design providing the performance offered by a high power CPU while also providing low current consumption. This low current consumption permits even a very small battery pack to power the radio for an entire (approximately 8 hour) shift. As a result, the radio with battery connected is light, lean and super compact. The preferred embodiment radio is the ideal portable for covert operations and any other applications where concealed and/or extremely miniaturized radios are required. For example, the preferred embodiment weighs less than 20 ounces (including battery), is slightly more than 1 inch deep, and is slender and lightweight enough to slip into a front shirt pocket.
Features provided by the presently preferred exemplary embodiment of the invention include:
Distribution of radio functions between a high-power/high-capability processor, a low-power/low-capability processor, and additional logic (e.g., an application specific integrated circuit) so that the high-power processor can be placed into a "software stand by" mode much of the time (i.e., except when actually needed); PA1 A current saving architecture for a radio using software standby ("SSB") mode with ASIC support to switch from IRQ (maskable) to NMI (non-maskable) interrupt inputs; PA1 Main CPU reads watchdog timer to accurately maintain system (real) time despite intermittent lapses into the sleep mode; PA1 A free running timer performs channel guard decode thus allowing simultaneous decode of channel guard and T99 signalling using the single low power processor; PA1 FIFO (first in first out) data buffer so that the high-power processor can sleep; PA1 Pulse width modulator is used to control the backlight brightness of the LCD display and thus save current; PA1 Low power processor decodes "low speed" digital signalling so high-power processor can sleep; PA1 Low power processor monitors synthesizer lock line to allow high-power processor to sleep; PA1 SSB is integrated into the high power processor operating system; PA1 Serial port is shared between micro-controllers to provide great flexibility in design and current savings (i.e., allowing the low-power processor to handle serial messages while allowing the high-power processor to sleep); and PA1 Board type resistors identify the type of board.